Method and apparatus for producing and treating novel elastomer composites

ABSTRACT

Elastomer masterbatch is processed in a continuous compounder having multiple parallel elongate rotors axially oriented in an elongate processing chamber. Optionally, additional materials are compounded into the masterbatch, e.g., additives, other elastomeric compositions, etc. Preferably, the masterbatch then is further processed in an open mill. Excellent control of Mooney Viscosity is achieved.  
     In certain preferred embodiments, elastomer composites are produced by novel continuous flow methods and apparatus in which fluid streams of particulate filler and elastomer latex are fed to the mixing zone of a coagulum reactor to form a coagulated mixture in semi-confined flow continuously from the mixing zone through a coagulum zone to a discharge end of the reactor. The particulate filler fluid is fed under high pressure to the mixing zone, such as to form a jet stream to entrain elastomer latex fluid sufficiently energetically to substantially completely coagulate the elastomer with the particulate filler prior to the discharge end without need of adding acid or salt solution or other coagulation step. The coagulated elastomer and particulate filler composite is fed into the aforesaid continuous compounder for processing and control of its moisture level and Mooney Viscosity. Novel elastomer composites are produced. Such novel elastomer composites combine material properties and characteristics, such as choice of filler, elastomer, level of filler loading, moisture level, Mooney Viscosity, balance between molecular weight and amount of bound rubber, and macro-dispersion not previously achieved.

FIELD OF THE INVENTION

[0001] The present invention is directed to novel methods and apparatusfor producing and treating elastomer composites, and to novel elastomercomposites produced using such methods and apparatus. More particularly,the invention is directed to continuous flow methods and apparatus forproducing and treating elastomer masterbatch of particulate fillerfinely dispersed in elastomer, for example, elastomer composites ofcarbon black particulate filler finely dispersed in natural rubber, andrubber materials and products formed of such masterbatch compositions.

BACKGROUND

[0002] Numerous products of commercial significance are formed ofelastomeric compositions wherein particulate filler is dispersed in anyof various synthetic elastomers, natural rubber or elastomer blends.Carbon black, for example, is widely used as a reinforcing agent innatural rubber and other elastomers. It is common to produce amasterbatch, that is, elastomer coagulated with carbon black or otherfiller and optionally containing various additives, such as extenderoil. Carbon black masterbatch can be prepared with different grades ofcarbon black, that is, carbon blacks which vary both in surface area perunit weight and in “structure.”

[0003] While a wide range of performance characteristics can be achievedemploying currently available materials and manufacturing techniques,there has been a longstanding need in the industry to developelastomeric compositions having improved properties and to reduce thecost and complexity of current manufacturing techniques. In particular,it is known for example that macro-dispersion level, that is, theuniformity of dispersion of the carbon black or other filler within theelastomer, can significantly impact performance characteristics. Forelastomeric compositions prepared by intensively mixing the carbon blackor other filler with natural rubber or other elastomer (such as in aBanbury mixer or the like), any increase in macro-dispersion requireslonger or more intensive mixing, with the consequent disadvantages ofincreased energy costs, manufacturing time, and similar concerns. Forcarbon black fillers of certain surface area and structurecharacteristics, dispersion beyond a certain degree has not beenpossible or commercially practicable using known mixing apparatus andtechniques. In addition, such prolonged or more intensive mixingdegrades the natural rubber or other elastomer by reducing its molecularweight, rendering the finished elastomeric compound undesirable forcertain applications.

[0004] In addition to dry mixing techniques, it is known to continuouslyfeed latex and a carbon black slurry to an agitated coagulation tank.Such “wet” techniques are used commonly with synthetic elastomer, suchas styrene-butadiene rubber (SBR). The coagulation tank contains acoagulant such as salt solution or an aqueous acid solution typicallyhaving a pH of about 2.5 to 4. The latex and carbon black slurry aremixed and then coagulated in the coagulation tank into small beads(typically a few millimeters in diameter) referred to as wet crumb. Thecrumb and acid (or saline) effluent are separated, typically by means ofa vibrating shaker screen or the like. The crumb is then dumped into asecond agitated tank where it is washed to achieve a neutral or nearneutral pH. Thereafter the crumb is subjected to additional vibratingscreen and drying steps and the like. Variations on this method havebeen suggested for the coagulation of natural and synthetic elastomers.In U.S. Pat. No. 4,029,633 to Hagopian et al, which like the presentinvention is assigned to Cabot Corporation, a continuous process for thepreparation of elastomer masterbatch is described. An aqueous slurry ofcarbon black is prepared and mixed with a natural or synthetic elastomerlatex. This mixture undergoes a so-called creaming operation, optionallyusing any of various known creaming agents. Following the creaming ofthe carbon black/latex mixture, it is subjected to a coagulation step.Specifically, the creamed carbon black/latex mixture is introduced as asingle coherent stream into the core of a stream of coagulating liquor.The solid stream of creamed carbon black/latex mixture is said toundergo shearing and atomizing by the stream of coagulating liquor priorto coagulation, being then passed to a suitable reaction zone forcompletion of the coagulation. Following such coagulation step, theremainder of the process is substantially conventional, involvingseparation of the crumb from the waste product “serum” and washing anddrying of the crumb. A somewhat similar process is described in U.S.Pat. No. 3,048,559 to Heller et al. An aqueous slurry of carbon black iscontinuously blended with a stream of natural or synthetic elastomerlatex. The two streams are mixed under conditions described as involvingviolent hydraulic turbulence and impact. As in the case of the Hagopianet al. patent mentioned above, the combined stream of carbon blackslurry and elastomer latex is subsequently coagulated by the addition ofan acid or salt coagulant solution.

[0005] Since good dispersion of a coagulating filler in the elastomerhas been recognized for some time as being important for achieving goodquality and consistent product performance, considerable effort has beendevoted to the development of procedures for assessing dispersionquality in rubber. Methods developed include, e.g. the Cabot DispersionChart and various image analysis procedures. Dispersion quality can bedefined as the state of mixing achieved. An ideal dispersion of carbonblack is the state in which the carbon black agglomerates (or pellets)are broken down into aggregates (accomplished by dispersive mixing)uniformly separated from each other in the elastomer (accomplished bydistributive mixing), with the surfaces of all the carbon blackaggregates completely wetted by the rubber matrix (usually referred toas incorporation).

[0006] Macro-dispersion of carbon black or other filler in uncurednatural rubber or other suitable elastomer can be assessed using imageanalysis of cut surface samples. Typically, five to ten arbitrarilyselected optical images are taken of the cut surface for image analysis.Knife marks and the like preferably are removed using a numericalfiltering technique. Cut surface image analysis thus providesinformation regarding the carbon black dispersion quality inside anatural rubber compound. Specifically, percent undispersed area D(%)indicates carbon black macro-dispersion quality. As macro-dispersionquality is degraded, percent undispersed area increases. Dispersionquality can be improved, therefore, by reducing the percent undispersedarea.

[0007] A commercial image analyzer such as the IBAS Compact model imageanalyzer available from Kontron Electronik GmbH (Munich, Germany) can beused to measure macro-dispersion of carbon black or other filler.Typically, in quantitative macro-dispersion tests used in the rubberindustry, the critical cut-off size is 10 microns. Defects larger thanabout 10 microns in size typically consist of undispersed carbon blackor other filler, as well as any grit or other contaminants, which canaffect both visual and functional performance. Thus, measuringmacro-dispersion involves measuring defects on a surface (generated bymicrotoming, extrusion or cutting) greater than 10 microns in size, bytotal area of such defects per unit area examined, using an imageanalysis procedure. Macro-dispersion D(%) is calculated as follows:${{Undispersed}\quad {{area}(\%)}} = {\frac{1}{A_{m}}{\sum\limits_{i = 1}^{m}{N_{i}\frac{\pi \quad D_{i}^{2}}{4}}}}$

[0008] where

[0009] A_(m)=Total sample surface area examined

[0010] N_(i)=Number of defects with size D_(i)

[0011] D=Diameter of circle having the same area as that of the defect(equivalent circle diameter)

[0012] m=number of images

[0013] There has long been a need in various industries for elastomericcompounds of particulate filler dispersed in suitable elastomer,especially, for example, carbon black dispersed in natural rubber,having improved macro-dispersion. As discussed above, improvedmacro-dispersion can provide correspondingly improved aesthetic andfunctional characteristics. Especially desirable are new elastomericcompounds of carbon black in natural rubber wherein improvedmacro-dispersion is achieved together with controlled Mooney Viscosity,higher molecular weight of the natural rubber, and higher amount ofbound rubber.

[0014] It is an object of the present invention to meet some or all ofthese long felt needs.

SUMMARY OF THE INVENTION

[0015] In accordance with a first aspect, a method of treating asubstantially coagulated masterbatch having a particulate filler and anelastomer includes the steps of feeding the masterbatch to a feed portof a continuous compounder having multiple rotors axially oriented in anelongate processing chamber; processing the masterbatch through theprocessing chamber of the continuous compounder by controlled operationof the rotors; and discharging the masterbatch from a discharge orificeof the continuous compounder. In certain preferred embodiments, themethod may also include the step of passing the masterbatch from thedischarge orifice of the continuous compounder through an open milland/or the step of compounding additional material into the masterbatchin the continuous compounder. In certain preferred embodiments, theadditional material may be selected from additional filler, additionalelastomer, a second masterbatch, oil and other additives. In certainpreferred embodiments, the continuous compounder dries the masterbatch.In certain preferred embodiments, the continuous compounder controls theMooney Viscosity of the masterbatch.

[0016] In accordance with another aspect, a continuous flow method ofproducing elastomer composite includes the steps of feeding a continuousflow of first fluid including elastomer latex to a mixing zone of acoagulum reactor defining an elongate coagulum zone extending from themixing zone to a discharge end; feeding a continuous flow of secondfluid having particulate filler under pressure to the mixing zone of thecoagulum reactor to form a mixture with the elastomer latex, the mixturepassing as a continuous flow to the discharge end and the particulatefiller being effective to coagulate the elastomer latex, wherein mixingof the first fluid and the second fluid within the mixing zone issufficiently energetic to substantially completely coagulate theelastomer latex with the particulate filler prior to the discharge end;discharging a substantially continuous flow of elastomer composite fromthe discharge end of the coagulum reactor; feeding the substantiallycontinuous flow of elastomer composite to a feed port of a continuouscompounder having multiple parallel rotors axially oriented in anelongate processing chamber; processing the elastomer composite throughthe processing chamber of the continuous compounder by controlledoperation of the rotors; and discharging the elastomer composite from adischarge orifice of the continuous compounder. In certain preferredembodiments, the method also includes the step of processing theelastomer composite from the discharge orifice of the continuouscompounder through an open mill.

[0017] In accordance with another aspect, an apparatus for producingelastomer composite of particulate filler dispersed in elastomer has acoagulum reactor defining a mixing zone and an elongate coagulum zoneextending from the mixing zone to a discharge end; latex feed means forfeeding elastomer latex fluid continuously to the mixing zone; fillerfeed means for feeding particulate filler fluid as a continuous jet intothe mixing zone to form a mixture with the elastomer latex fluidtraveling from the mixing zone to the discharge end of the coagulumzone, wherein the distance between the mixing zone and the discharge endis sufficient to permit substantially complete coagulation of theelastomer latex prior to the discharge end; and a continuous compounderhaving a feed port operatively connected to the discharge end of thecoagulum zone for receiving the coagulated mixture of elastomer latexand particulate filler, a discharge orifice, an elongate processingchamber, and a plurality of rotors axially oriented within theprocessing chamber. In certain preferred embodiments, the apparatusfurther has conveying means for conveying a substantially continuousflow of elastomer composite from the discharge end of the coagulum zoneto the feed port of the continuous compounder.

[0018] In accordance with another aspect, an elastomer composite hassubstantially coagulated elastomer in which particulate filler has beendispersed by feeding a continuous flow of first fluid having elastomerlatex to a mixing zone of a coagulum reactor defining an elongatecoagulum zone extending from the mixing zone to a discharge end; feedinga continuous flow of second fluid having particulate filler underpressure to the mixing zone of the coagulum reactor to form a mixturewith the elastomer latex, the mixture passing as a continuous flow tothe discharge end, and the particulate filler being effective tocoagulate the elastomer latex, wherein mixing of the first fluid and thesecond fluid within the mixing zone is sufficiently energetic tosubstantially completely coagulate the elastomer latex with theparticulate filler prior to the discharge end; discharging asubstantially continuous flow of elastomer composite from the dischargeend of the coagulum reactor; feeding the elastomer composite from thedischarge end of the coagulum reactor to a continuous compounder havingmultiple parallel elongate rotors axially oriented in an elongateprocessing chamber; processing the masterbatch through the processingchamber of the continuous compounder by controlled operation of therotors; and discharging the masterbatch from a discharge orifice of thecontinuous compounder.

[0019] In accordance with another aspect, masterbatch is processed in acontinuous compounder as described above along with the addition ofother materials. Specifically, the additional materials may beadditional filler; additional elastomers; additional masterbatch,comprising elastomer composite and carbon black or other filler; any ofvarious known additives used in elastomer composites, such asantioxidants, antiozonants, plasticizers, processing aids (e.g., liquidpolymers, oils and the like), resins, flame-retardants, extender oils,lubricants, and a mixture of any of them; and a vulcanization system, ora mixture of any of these.

[0020] In accordance with another aspect, a method for preparingelastomer masterbatch comprises feeding simultaneously a particulatefiller fluid and an elastomer latex fluid to a mixing zone of a coagulumreactor, followed by further processing in a de-watering extruder andcontinuous compounder, as disclosed above. Most preferably the coagulumreactor , de-watering extruder and the continuous compounder operatetogether in a continuous flow production line. A coagulum zone of thecoagulum reactor extends from the mixing zone, preferably progressivelyincreasing in cross-sectional area in the downstream direction from anentry end to a discharge end. The elastomer latex may be either naturalor synthetic and the particulate filler fluid comprises carbon black orother particulate filler effective to coagulate the latex. Theparticulate filler fluid is fed to the mixing zone preferably as acontinuous, high velocity jet of injected fluid, while the latex fluidis fed at low velocity. The velocity, flow rate and particulateconcentration of the particulate filler fluid are sufficient to causehigh shear mixing with the latex fluid and flow turbulence of themixture within at least an upstream portion of the coagulum zone, so asto substantially completely coagulate the elastomer latex with theparticulate filler prior to the discharge end. Substantially completecoagulation is thus achieved, in accordance with preferred embodiments,without the need of employing an acid or salt coagulation agent. Thecoagulum reactor is discussed in detail in commonly owned and copendingU.S. application Ser. No. 08/823,411 and in Published PCT ApplicationSerial Number PCT/US97/05276, both of which are incorporated herein byreference. The masterbatch from the coagulum reactor is fed through ade-watering extruder to remove the bulk of the water from themasterbatch and then into a feed port of the continuous compounderdisclosed above, preferably in a continuous flow stream from thecoagulum reactor. The continuous compounder dries the elastomermasterbatch, provides control over the Mooney Viscosity of the elastomermasterbatch and, in certain preferred embodiments, control over othercharacteristics and performance properties of the masterbatch viamanipulation of continuous compounder operating parameters, includingrotor speed, throughput rate, discharge orifice opening size, dischargeorifice temperature and processing chamber temperature. The masterbatchmay, in accordance with certain preferred embodiments, optionally befurther processed after the continuous compounder by an open mill tofurther control the Mooney Viscosity of the masterbatch. This isespecially advantageous, since the elastomer masterbatch produced by thecoagulum reactor may have a Mooney Viscosity which is too high for usein certain applications. Further processing of the masterbatch by thecontinuous compounder and the open mill is now found to provideexcellent product control to achieve a desired Mooney Viscosity andmoisture level.

[0021] In especially preferred embodiments, the above disclosedde-watering extruder is connected to the coagulum reactor by a conveyoror conduit for carrying masterbatch from the coagulum reactor to thede-watering extruder, and the continuous compounder is directlydownstream of the de-watering extruder, such that the masterbatch isproduced and treated in a continuous flow process. Thus, a continuousprocess line is created for the formation and treatment of elastomermasterbatch, which provides for significantly enhanced economies ofproduction. Use of the continuous compounder with a de-watering extruderand coagulum reactor in a continuous process line can facilitatecontrolling and changing operating parameters of the masterbatchproduction and treatment line without interrupting the continuousprocess line.

[0022] In accordance with an apparatus aspect, a coagulum reactor,de-watering extruder and continuous compounder described above arecoupled in a masterbatch production and treatment line. In accordancewith certain preferred embodiments, an open mill is provided to cool theelastomer masterbatch and further control its Mooney Viscosity after itpasses through the continuous compounder.

[0023] In accordance with another apparatus aspect, means are providedfor feeding elastomer latex fluid to the mixing zone of the aforesaidcoagulum reactor, preferably under low pressure, substantially laminartype flow conditions, and means are provided for simultaneously feedingparticulate filler fluid to the mixing zone under pressure sufficient tocreate a jet of adequate velocity or kinetic energy to entrain theelastomer latex, as described above, and achieve coagulation before theproduct flowing downstream from the mixing zone reaches the dischargeend of the coagulum reactor. In accordance with certain preferredembodiments described in detail below, means for feeding the elastomerlatex fluid and separate means for feeding the particulate filler fluideach may comprise a feed channel in a mixing head integral with asubstantially tubular member defining the coagulum zone. The mixing zonemay be provided at the junction of such feed channels within the mixinghead. In accordance with certain preferred embodiments, the mixing zoneis simply a coaxial extension of the coagulum zone. Progressive increasein the cross-sectional area of the coagulum reactor is continuous incertain preferred embodiments and is step-wise in other preferredembodiments. A de-watering extruder and continuous compounder arepositioned downstream of the coagulum reactor to further process theelastomer masterbatch, providing drying and control of the MooneyViscosity and other physical properties and performance characteristicsof the elastomer masterbatch. In certain preferred embodiments, an openmill may be coupled to the discharge orifice of the continuouscompounder, either directly or via a conveyor or other conduit, toprovide yet further treatment of the elastomer masterbatch. Additionaloptional and preferred features of the apparatus disclosed here forcontinuous flow production of elastomer masterbatch are discussed in thedetailed description below.

[0024] In accordance with yet another aspect, elastomer composites areprovided as a product of the process or apparatus disclosed above. Inaccordance with preferred embodiments, novel elastomer composites areprovided having macro-dispersion level of the particulate filler,molecular weight of the elastomer, particulate loading level, choice ofparticulate filler (including, for example, carbon black fillers ofexceptionally high surface area and low structure), controlled MooneyViscosity and/or other physical properties or performancecharacteristics not previously achieved. Additionally, a suitablebalance can be obtained between the molecular weight and bound rubber ofthe masterbatch for a given Mooney Viscosity. In that regard, themethods and apparatus disclosed here can achieve excellentmacro-dispersion, even of certain fillers, such as carbon blacks havinga structure to surface area ratio DBP:CTAB less than 1.2 and even lessthan 1, in elastomers such as natural rubber, while minimizingdegradation of the molecular weight of the elastomer and highlycontrolled Mooney Viscosity. In accordance with yet other aspects of theinvention, intermediate products are provided as well as final productswhich are formed of the elastomer composites produced by the method orapparatus disclosed here, e.g., tires and tire components. Furtherexamples of such final products are listed below.

[0025] These and other aspects and advantages of various embodiments ofthe invention will be further understood in view of the followingdetailed discussion of certain preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following discussion of certain preferred embodiments willmake reference to the appended drawings wherein:

[0027]FIG. 1 is a schematic flow chart illustration of the apparatus andmethod for preparing elastomer masterbatch in accordance with certainpreferred embodiments of the present invention;

[0028]FIG. 2 is an elevation view, partly schematic, of a preferredembodiment consistent with the schematic flow chart illustration of FIG.1;

[0029]FIG. 3 is an elevation view, partially schematic, of analternative preferred embodiment consistent with the schematic flowchart illustration of FIG. 1;

[0030]FIG. 4 is an elevation view, partially in section, of the mixinghead/coagulum reactor assembly of the embodiment of FIG. 3;

[0031]FIG. 5 is an elevation view, partially in section, correspondingto the view of FIG. 4, illustrating an alternative preferred embodiment;

[0032]FIG. 6 is a section view taken through line 6-6 of FIG. 5;

[0033]FIG. 7 is a section view of a mixing head suitable for use in analternative preferred embodiment;

[0034]FIG. 8 is a schematic flowchart of a portion of an alternativeembodiment of the masterbatch production line of FIG. 1 showing thecontinuous compounder of FIG. 1 in section; and

[0035]FIG. 9 is a schematic flowchart of a portion of an alternativeembodiment of the apparatus and method of FIG. 1.

[0036] It should be understood that the appended drawings are notnecessarily precisely to scale. Certain features may have been enlargedor reduced for convenience or clarity of illustration. Directionalreferences used in the following discussion are based on the orientationof components illustrated in the drawings unless otherwise stated orotherwise clear from the context. In general, apparatus in accordancewith different embodiments of the invention can be employed in variousarrangements. It will be within the ability of those skilled in the art,given the benefit of the present disclosure, to determine appropriatedimensions and orientations for apparatus of the invention employingroutine technical skills and taking into account well-known factorsparticular to the intended application, such as desired productionvolumes, material selection, duty cycle, and the like. Reference numbersused in one drawing may be used in other drawings for the same featureor element.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

[0037] The following is a detailed description of certain preferredembodiments of the present invention and is not intended to limit thepresent invention to the embodiments described below.

[0038] By virtue of the method and apparatus disclosed here, wetelastomer masterbatch can be processed to remove moisture, reduce itsMooney Viscosity, and/or to compound it with other materials. Preferablythe masterbatch is produced in a continuous flow process involvingmixture of elastomer latex and particulate filler fluids at turbulencelevels and flow control conditions sufficient to achieve coagulationeven without use of traditional coagulating agents. In fact, it will beimmediately recognized to be of great commercial benefit that elastomermasterbatch crumb is achieved, that is, coagulated latex is achieved,without the need for either intensive dry mastication of elastomer withfiller or exposing a liquid latex/particulate composition to a stream ortank of coagulant. Thus, in routine commercial implementation the costand complexity of employing acid coagulation solutions can be avoided.Prior techniques involving premixing of latex and particulate, such asin the above-mentioned Heller et al. patent and Hagopian et al. patentdo not even recognize the possibility of achieving coagulation withoutexposing the latex/particulate mixture to the usual coagulant solutionwith its attendant cost and waste disposal disadvantages. Elastomermasterbatch produced by this continuous flow process may have a MooneyViscosity and moisture level which are too high for certainapplications. The use of a de-watering extruder and continuouscompounder, described in greater detail below, dries the elastomermasterbatch and controls its Mooney Viscosity, while optimizingmolecular weight and bound rubber.

[0039] Feed rates of latex fluid and particulate filler fluid to themixing zone of the coagulum reactor can be precisely metered to achievehigh yield rates, with little free latex and little undispersed fillerin the product crumb at the discharge end of the coagulum reactor.Without wishing to be bound by theory, it presently is understood that aquasi-mono-phase system is established in the mixing zone except thatcoagulum solids are being formed there and/or downstream thereof in thecoagulum zone. Extremely high feed velocity of the particulate fillerfluid into the mixing zone of the coagulum reactor and velocitydifferential relative the latex fluid feed are believed to besignificant in achieving sufficient turbulence, i.e., sufficientlyenergetic shear of the latex by the impact of the particulate fillerfluid jet for thorough mixing and dispersion of the particulate into thelatex fluid and coagulation. High mixing energies yield productmasterbatch crumb with excellent dispersion, together with controlledproduct delivery. The coagulum is created and then formed into adesirable extrudate.

[0040] Certain preferred embodiments are discussed below, of methods andapparatus for producing the novel elastomer composites disclosed here.While various preferred embodiments of the invention can employ avariety of different fillers and elastomers, certain portions of thefollowing detailed description of method and apparatus aspects of theinvention will, for convenience, describe their use primarily inproducing masterbatch comprising natural rubber and carbon black. Itwill be within the ability of those skilled in the art, given thebenefit of this disclosure, to employ the method and apparatus disclosedhere in accordance with the principles of operation discussed below toproduce masterbatch comprising a number of alternative or additionalelastomers, fillers and other materials. In brief, such methods forpreparing elastomer masterbatch involve feeding simultaneously a slurryof carbon black or other filler and a natural rubber latex fluid orother suitable elastomer fluid to a mixing zone of a coagulum reactor. Acoagulum zone extends from the mixing zone, preferably progressivelyincreasing in cross-sectional area in the downstream direction from anentry end to a discharge end. The slurry is fed to the mixing zonepreferably as a continuous, high velocity jet of injected fluid, whilethe natural rubber latex fluid is fed at relatively low velocity. Thehigh velocity, flow rate and particulate concentration of the fillerslurry are sufficient to cause mixture and high shear of the latexfluid, flow turbulence of the mixture within at least an upstreamportion of the coagulum zone, and substantially completely coagulate theelastomer latex prior to the discharge end. Substantially completecoagulation can thus be achieved, in accordance with preferredembodiments, without the need of employing an acid or salt coagulationagent. The preferred continuous flow method of producing the elastomercomposites comprises the continuous and simultaneous feeding of thelatex fluid and filler slurry to the mixing zone of the coagulumreactor, establishing a continuous, semi-confined flow of a mixture ofthe latex and filler slurry in the coagulum zone. Elastomer compositecrumb in the form of “worms” or globules are discharged from thedischarge end of the coagulum reactor as a substantially constant flowconcurrently with the on-going feeding of the latex and carbon blackslurry streams into the mixing zone of the coagulum reactor. Notably,the plug-type flow and atmospheric or near atmospheric pressureconditions at the discharge end of the coagulum reactor are highlyadvantageous in facilitating control and collection of the elastomercomposite product, such as for immediate or subsequent furtherprocessing steps. Feed rates of the natural rubber latex fluid andcarbon black slurry to the mixing zone of the coagulum reactor can beprecisely metered to achieve high yield rates, with little free latexand little undispersed carbon black in the product crumb at thedischarge end of the coagulum reactor. Without wishing to be bound bytheory, it presently is understood that a quasi-mono-phase system isestablished in the mixing zone except that coagulum solids are beingformed there and/or downstream thereof in the coagulum zone. Extremelyhigh feed velocity of the carbon black slurry into the mixing zone ofthe coagulum reactor and velocity differential relative the naturalrubber latex fluid feed are believed to be significant in achievingsufficient turbulence, i.e., sufficiently energetic shear of the latexby the impact of the particulate filler fluid jet, for thorough mixingand dispersion of the particulate into the latex fluid and coagulation.High mixing energies yield the novel product with excellentmacro-dispersion, together with controlled product delivery. Thecoagulum is created and then formed into a desirable extrudate. The bulkof the water in the extrudate is then preferably removed by ade-watering extruder (e.g., from approximately 80% water content toapproximately 15% to 25% water content) and further processed by acontinuous compounder to dry the elastomer masterbatch to a desiredlevel (e.g., below approximately 1% water content) and control itsMooney Viscosity. In certain preferred embodiments, the masterbatch isthen processed by an open mill to further control the Mooney Viscosityof the elastomer masterbatch.

[0041] The aforesaid preferred apparatus and techniques for producingthe elastomer composites disclosed here are discussed in conjunctionwith the appended drawings, wherein a continuous flow method ofproducing elastomer masterbatch employs a continuous, semi-confined flowof elastomer latex, for example, natural rubber latex (field latex orconcentrate) mixed with a filler slurry, for example, an aqueous slurryof carbon black, in a coagulum reactor forming an elongate coagulum zonewhich extends, preferably with progressively increasing cross-sectionalarea, from an entry end to a discharge end. The term “semi-confined”flow refers to a highly advantageous feature. As used here the term isintended to mean that the flow path followed by the mixed latex fluidand filler slurry within the coagulum reactor is closed or substantiallyclosed upstream of the mixing zone and is open at the opposite,downstream end of the coagulum reactor, that is, at the discharge end ofthe coagulum reactor. Turbulence conditions in the upstream portion ofthe coagulum zone are maintained in on-going, at least quasi-steadystate fashion concurrently with substantially plug flow-type conditionsat the open discharge end of the coagulum reactor. The discharge end is“open” at least in the sense that it permits discharge of coagulum,generally at or near atmospheric pressure and, typically, by simplegravity drop (optionally within a shrouded or screened flow path) intosuitable collection means, such as a hopper connected to a de-wateringextruder. Thus, the semi-confined flow results in a turbulence gradientextending axially or longitudinally within at least a portion of thecoagulum reactor. Without wishing to be bound by theory, it presently isunderstood that the coagulum zone is significant in permitting highturbulence mixing and coagulation in an upstream portion of the coagulumreactor, together with substantially plug-type discharge flow of a solidproduct at the discharge end. Injection of the carbon black or otherfiller slurry as a continuous jet into the mixing zone occurs inon-going fashion simultaneously with ease of collection of the elastomermasterbatch crumb discharged under substantially plug-type flowconditions and generally ambient pressure at the discharge end of thecoagulum reactor. Similarly, axial velocities of the slurry through theslurry nozzle into the mixing zone and, typically, at the upstream endof the coagulum zone are substantially higher than at the discharge end.Axial velocity of the slurry will typically be several hundred feet persecond as it enters the mixing zone, preferably from a small bore,axially oriented feed tube in accordance with preferred embodimentsdiscussed below. The axial velocity of the resultant flow at the entryend of a coagulum reactor with expanding cross-sectional area in atypical application may be, for example, 5 to 20 feet per second, andmore usually 7 to 15 feet per second. At the discharge end, in contrastagain, axial velocity of the masterbatch crumb product being dischargedthere will in a typical application be approximately 1 to 10 feet persecond, and more generally 2 to 5 feet per second. Thus, the aforesaidsemi-confined turbulent flow achieves the highly significant advantagethat natural rubber or other elastomer latex is coagulated by mixturewith carbon black or other filler even in the absence of subsequenttreatment in a stream or tank of acid, salt or other coagulant solution,with controlled, preferably quasi-molded product delivery from thecoagulum reactor for subsequent processing.

[0042] It should also be recognized in this regard that the turbulenceof the flow lessens along the coagulum reactor toward the discharge end.Substantial plug flow of a solid product is achieved prior to thedischarge end, dependent upon such factors as percent of capacityutilization, selection of materials and the like. Reference here to theflow being substantially plug flow at or before the discharge end of thecoagulum reactor should be understood in light of the fact that the flowat the discharge end is composed primarily or entirely of masterbatchcrumb, that is, globules or “worms” of coagulated elastomer masterbatch.The crumb is typically quasi-molded to the inside shape of the coagulumzone at the point along the coagulum zone at which flow becamesubstantially plug flow. The ever-advancing mass of “worms” or globulesadvantageously have plug-type flow in the sense that they are travelinggenerally or primarily axially toward the discharge end and at any pointin time in a given cross-section of the coagulum zone near the dischargeend have a fairly uniform velocity, such that they are readily collectedand controlled for further processing. Thus, the fluid phase mixingaspect disclosed here can advantageously be carried out at steady stateor quasi-steady state conditions, resulting in high levels of productuniformity.

[0043] A preferred embodiment of the method and apparatus disclosed hereis illustrated schematically in FIG. 1. Those skilled in the art willrecognize that the various aspects of system configuration, componentselection and the like will depend to some extent on the particularcharacteristics of the intended application. Thus, for example, suchfactors as maximum system through-put capacity and material selectionflexibility will influence the size and layout of system components. Ingeneral, such considerations will be well within the ability of thoseskilled in the art given the benefit of the present disclosure. Thesystem illustrated in FIG. 1 is seen to include means for feedingnatural rubber latex or other elastomer latex fluid at low pressure andlow velocity continuously to a mixing zone of a coagulum reactor. Moreparticularly, a latex pressure tank 10 is shown, to hold the feed supplyof latex under pressure. Alternatively, a latex storage tank can beused, equipped with a peristaltic pump or series of pumps or othersuitable feed means adapted to hold elastomer latex fluid to be fed viafeed line 12 to a mixing zone of a coagulum reactor 14. Latex fluid intank 10 may be held under air or nitrogen pressure or the like, suchthat the latex fluid is fed to the mixing zone at a line pressure ofpreferably less than 10 psig, more preferably about 2-8 psig, andtypically about 5 psig. The latex feed pressure and the flow lines,connections, etc., of the latex feed means should be arranged tomaintain shear in the flowing latex fluid as low as reasonably possible.Preferably all flow lines, for example, are smooth, with only largeradius turns, if any, and smooth or flared line-to-lineinterconnections. The pressure is selected to yield the desired flowvelocity into the mixing zone; an example of a useful flow velocity isno more than about 12 feet per second.

[0044] Suitable elastomer latex fluids include both natural andsynthetic elastomer latices and latex blends. The latex must, of course,be suitable for coagulation by the selected particulate filler and mustbe suitable for the intended purpose or application of the final rubberproduct. It will be within the ability of those skilled in the art toselect suitable elastomer latex or a suitable blend of elastomer laticesfor use in the methods and apparatus disclosed here, given the benefitof this disclosure. Exemplary elastomers include, but are not limitedto, rubbers, polymers (e.g., homopolymers, copolymers and/orterpolymers) of 1,3-butadiene, styrene, isoprene, isobutylene,2,3-dimethyl-1,3-butadiene, acrylonitrile, ethylene, and propylene andthe like. The elastomer may have a glass transition temperature (Tg) asmeasured by differential scanning calorimetry (DSC) ranging from about−120° C. to about 0° C. Examples include, but are not limited to,styrene-butadiene rubber (SBR), natural rubber and its derivatives suchas chlorinated rubber, polybutadiene, polyisoprene,poly(stryeneco-butadiene) and the oil extended derivatives of any ofthem. Blends of any of the foregoing may also be used. The latex may bein an aqueous carrier liquid. Alternatively, the liquid carrier may be ahydrocarbon solvent. In any event, the elastomer latex fluid must besuitable for controlled continuous feed at appropriate velocity,pressure and concentration into the mixing zone. Particular suitablesynthetic rubbers include: copolymers of from about 10 to about 70percent by weight of styrene and from about 90 to about 30 percent byweight of butadiene such as copolymer of 19 parts styrene and 81 partsbutadiene, a copolymer of 30 parts styrene and 70 parts butadiene, acopolymer of 43 parts styrene and 57 parts butadiene and a copolymer of50 parts styrene and 50 parts butadiene; polymers and copolymers ofconjugated dienes such as polybutadiene, polyisoprene, polychloroprene,and the like, and copolymers of such conjugated dienes with an ethylenicgroup-containing monomer copolymerizable therewith such as styrene,methyl styrene, chlorostyrene, acrylonitrile, 2-vinyl-pyridine,5-methyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine,2-methyl-5-vinylpyridine, allyl-substituted acrylates, vinyl ketone,methyl isopropenyl ketone, methyl vinyl either, alphamethylenecarboxylic acids and the esters and amides thereof such as acrylic acidand dialkylacrylic acid amide. Also suitable for use herein arecopolymers of ethylene and other high alpha olefins such as propylene,butene-1 and pentene-1. As noted further below, the rubber compositionsof the present invention can contain, in addition to the elastomer andfiller, a coupling agent, and optionally, various processing aids, oilextenders and antidegradents.

[0045] In that regard, it should be understood that the elastomercomposites disclosed here include vulcanized compositions (VR),thermoplastic vulcanizates (TPV), thermoplastic elastomers (TPE) andthermoplastic polyolefins (TPO). TPV, TPE, and TPO materials are furtherclassified by their ability to be extruded and molded several timeswithout loss of performance characteristics.

[0046] Where the elastomer latex comprises natural rubber latex, thenatural rubber latex can comprise field latex or latex concentrate(produced, for example, by evaporation, centrifugation or creaming). Thenatural rubber latex must, of course, be suitable for coagulation by thecarbon black. The latex is provided typically in an aqueous carrierliquid. Alternatively, the liquid carrier may be a hydrocarbon solvent.In any event, the natural rubber latex fluid must be suitable forcontrolled continuous feed at appropriate velocity, pressure andconcentration into the mixing zone. The well known instability ofnatural rubber latex is advantageously accommodated, in that it issubjected to relatively low pressure and low shear throughout the systemuntil it is entrained into the aforesaid semi-confined turbulent flowupon encountering the extraordinarily high velocity and kinetic energyof the carbon black slurry in the mixing zone. In certain preferredembodiments, for example, the natural rubber is fed to the mixing zoneat a pressure of about 5 psig, at a feed velocity in the range of about3-12 ft. per second, more preferably about 4-6 ft. per second. Selectionof a suitable latex or blend of latices will be well within the abilityof those skilled in the art given the benefit of the present disclosureand the knowledge of selection criteria generally well recognized in theindustry.

[0047] The particulate filler fluid, for example, carbon black slurry,is fed to the mixing zone at the entry end of coagulum reactor 14 viafeed line 16. The slurry may comprise any suitable filler in a suitablecarrier fluid. Selection of the carrier fluid will depend largely uponthe choice of particulate filler and upon system parameters. Bothaqueous and non-aqueous liquids may be used, with water being preferredin many embodiments in view of its cost, availability and suitability ofuse in the production of carbon black and certain other filler slurries.

[0048] When a carbon black filler is used, selection of the carbon blackwill depend largely upon the intended use of the elastomer masterbatchproduct. Optionally, the carbon black filler can include also anymaterial which can be slurried and fed to the mixing zone in accordancewith the principles disclosed here. Other suitable particulate fillersinclude, for example, conductive fillers, reinforcing fillers, fillerscomprising short fibers (typically having an L/D aspect ratio less than40), flakes, etc. Thus, exemplary particulate fillers which can beemployed in producing elastomer masterbatch in accordance with themethods and apparatus disclosed here, are carbon black, fumed silica,precipitated silica, coated carbon black, chemically functionalizedcarbon blacks, such as those having attached organic groups, andsilicon-treated carbon black, either alone or in combination with eachother. Suitable chemically functionalized carbon blacks include thosedisclosed in International Application No. PCT/US95/16194 (WO 9618688),the disclosure of which is hereby incorporated by reference. Insilicon-treated carbon black, a silicon containing species such as anoxide or carbide of silicon, is distributed through at least a portionof the carbon black aggregate as an intrinsic part of the carbon black.Conventional carbon blacks exist in the form of aggregates, with eachaggregate consisting of a single phase, which is carbon. This phase mayexist in the form of a graphitic crystallite and/or amorphous carbon,and is usually a mixture of the two forms. As discussed elsewhereherein, carbon black aggregates may be modified by depositingsilicon-containing species, such as silica, on at least a portion of thesurface of the carbon black aggregates. The result may be described assilicon-coated carbon blacks. The materials described herein assilicon-treated carbon blacks are not carbon black aggregates which havebeen coated or otherwise modified, but actually represent a differentkind of aggregate. In the silicon-treated carbon blacks, the aggregatescontain two phases. One phase is carbon, which will still be present asgraphitic crystallite and/or amorphous carbon, while the second phase issilica (and possibly other silicon-containing species). Thus, thesilicon-containing species phase of the silicon-treated carbon black isan intrinsic part of the aggregate; it is distributed throughout atleast a portion of the aggregate. It will be appreciated that themultiphase aggregates are quite different from the silica-coated carbonblacks mentioned above, which consist of pre-formed, single phase carbonblack aggregates having silicon-containing species deposited on theirsurface. Such carbon blacks may be surface-treated in order to place asilica functionality on the surface of the carbon black aggregate. Inthis process, an existing aggregate is treated so as to deposit or coatsilica (as well as possibly other silicon-containing species) on atleast a portion of the surface of the aggregate. For example, an aqueoussodium silicate solution may be used to deposit amorphous silica on thesurface of carbon black aggregates in an aqueous slurry at high pH, suchas 6 or higher, as discussed in Japanese Unexamined Laid-Open (Kokai)Publication No. 63-63755. More specifically, carbon black may bedispersed in water to obtain an aqueous slurry consisting, for example,of about 5% by weight carbon black and 95% by weight water. The slurryis heated to above about 70° C., such as to 85°-95° C., and the pHadjusted to above 6, such as to a range of 10-11, with an alkalisolution. A separate preparation is made of sodium silicate solution,containing the amount of silica which is desired to be deposited on thecarbon black, and an acid solution to bring the sodium silicate solutionto a neutral pH. The sodium silicate and acid solutions are addeddropwise to the slurry, which is maintained at its starting pH valuewith acid or alkali solution as appropriate. The temperature of thesolution is also maintained. A suggested rate for addition of the sodiumsilicate solution is to calibrate the dropwise addition to add about 3weight percent silicic acid, with respect to the total amount of carbonblack, per hour. The slurry should be stirred during the addition, andafter its completion for from several minutes (such as 30) to a fewhours (i.e., 2-3). In contrast, silicon-treated carbon blacks may beobtained by manufacturing carbon black in the presence of volatizablesilicon-containing compounds. Such carbon blacks are preferably producedin a modular or “staged” furnace carbon black reactor having acombustion zone followed by a zone of converging diameter, a feed stockinjection zone with restricted diameter, and a reaction zone. A quenchzone is located downstream of the reaction zone. Typically, a quenchingfluid, generally water, is sprayed into the stream of newly formedcarbon black particles flowing from the reaction zone. In producingsilicon-treated carbon black, the aforesaid volatizablesilicon-containing compound is introduced into the carbon black reactorat a point upstream of the quench zone. Useful compounds are volatizablecompounds at carbon black reactor temperatures. Examples include, butare not limited to, silicates such as tetraethoxy orthosilicate (TEDS)and tetramethoxy orthosilicate, silanes such as, tetrachloro silane, andtrichloro methylsilane; and volatile silicone polymers such asoctamethylcyclotetrasiloxane (OMTS). The flow rate of the volatilizablecompound will determine the weight percent of silicon in the treatedcarbon black. The weight percent of silicon in the treated carbon blacktypically ranges from about 0.1 percent to 25 percent, preferably about0.5 percent to about 10 percent, and more preferably about 2 percent toabout 6 percent. The volatizable compound may be pre-mixed with thecarbon black-forming feed stock and introduced with the feed stock intothe reaction zone. Alternatively, the volatizable compound may beintroduced to the reaction zone separately, either upstream ordownstream from the feed stock injection point.

[0049] As noted above, additives may be used, and in this regardcoupling agents useful for coupling silica or carbon black should beexpected to be useful with the silicon-treated carbon blacks. Carbonblacks and numerous other suitable particulate fillers are commerciallyavailable and are known to those skilled in the art.

[0050] Selection of the particulate filler or mixture of particulatefillers will depend largely upon the intended use of the elastomermasterbatch product. As used here, particulate filler can include anymaterial which can be slurried and fed to the mixing zone in accordancewith the principles disclosed here. Suitable particulate fillersinclude, for example, conductive fillers, reinforcing fillers, fillerscomprising short fibers (typically having an L/D aspect ratio less than40), flakes, etc. In addition to the carbon black and silica-typefillers mentioned above, fillers can be formed of clay, glass, polymer,such as aramid fiber, etc. It will be within the ability of thoseskilled in the art to select suitable particulate fillers for use in themethod and apparatus disclosed here given the benefit of the presentdisclosure, and it is expected that any filler suitable for use inelastomer compositions may be incorporated into the elastomer compositesusing the teachings of the present disclosure. Of course, blends of thevarious particulate fillers discussed herein may also be used.

[0051] Preferred embodiments of the invention consistent with FIG. 1 areespecially well adapted to preparation of particulate filler fluidcomprising aqueous slurries of carbon black. In accordance with knownprinciples, it will be understood that carbon blacks having lowersurface area per unit weight must be used in higher concentration in theparticulate slurry to achieve the same coagulation efficacy as lowerconcentrations of carbon black having higher surface area per unitweight. Agitated mixing tank 18 receives water and carbon black, e.g.,optionally pelletized carbon black, to prepare an initial mixture fluid.Such mixture fluid passes through discharge orifice 20 into fluid line22 equipped with pumping means 24, such as a diaphragm pump or the like.Line 28 passes the mixture fluid to colloid mill 32, or alternatively apipeline grinder or the like, through intake port 30. The carbon blackis dispersed in the aqueous carrier liquid to form a dispersion fluidwhich is passed through outlet port 31 and fluid line 33 to ahomogenizer 34. Pumping means 36, preferably comprising a progressingcavity pump or the like is provided in line 33. Homogenizer 34 morefinely disperses the carbon black in the carrier liquid to form thecarbon black slurry which is fed to the mixing zone of the coagulumreactor 14. It has an inlet port 37 in fluid communication with line 33from the colloid mill 32. The homogenizer 34 may preferably comprise,for example, a Microfluidizer® system commercially available fromMicrofluidics International Corporation (Newton, Mass., USA). Alsosuitable are homogenizers such as models MS18, MS45 and MC120 Serieshomogenizers available from the APV Homogenizer Division of APV Gaulin,Inc. (Wilmington, Mass., USA). Other suitable homogenizers arecommercially available and will be apparent to those skilled in the artgiven the benefit of the present disclosure. Typically, carbon black inwater prepared in accordance with the above described system will haveat least about 90% agglomerates less than about 30 microns, morepreferably at least about 90% agglomerates less than about 20 microns insize. Preferably, the carbon black is broken down to an average size of5-15 microns, e.g., about 9 microns. Exit port 38 passes the carbonblack slurry from the homogenizer to the mixing zone through feed line16. The slurry may reach 10,000 to 15,000 psi in the homogenizer stepand exit the homogenizer at about 600 psi or more. Preferably, a highcarbon black content is used to reduce the task of removing excess wateror other carrier. Typically, about 10 to 30 weight percent carbon blackis preferred. Those skilled in the art will recognize, given the benefitof this disclosure, that the carbon black content (in weight percent) ofthe slurry and the slurry flow rate to the mixing zone should becoordinated with the natural rubber latex flow rate to the mixing zoneto achieve a desired carbon black content (in phr) in the masterbatch.The carbon black content will be selected in accordance with knownprinciples to achieve material characteristics and performanceproperties suited to the intended application of the product. Typically,for example, carbon blacks of CTAB value 10 or more are used insufficient amount to achieve carbon black content in the masterbatch ofat least about 30 phr.

[0052] The slurry preferably is used in masterbatch productionimmediately upon being prepared. Fluid conduits carrying the slurry andany optional holding tanks and the like, should establish or maintainconditions which substantially preserve the dispersion of the carbonblack in the slurry. That is, substantial reaglomeration or settling outof the particulate filler in the slurry should be prevented or reducedto the extent reasonably practical. Preferably all flow lines, forexample, are smooth, with smooth line-to-line interconnections.Optionally, an accumulator is used between the homogenizer and themixing zone to reduce fluctuations in pressure or velocity of the slurryat the slurry nozzle tip in the mixing zone.

[0053] Natural rubber latex fluid or other elastomer latex fluid passedto the mixing zone via feed line 12 and carbon black slurry fed to themixing zone via feed line 16 under proper process parameters asdiscussed above, can produce a novel elastomer composite, specifically,elastomer masterbatch crumb. Means may also be provided forincorporating various additives into the elastomer masterbatch. Anadditive fluid comprising one or more additives may be fed to the mixingzone as a separate feed stream. One or more additives also may bepre-mixed, if suitable, with the carbon black slurry or, more typically,with the elastomer latex fluid. Additives also can be mixed into themasterbatch subsequently, e.g., by dry mixing techniques. Numerousadditives are well known to those skilled in the art and include, forexample, antioxidants, antiozonants, plasticizers, processing aids(e.g., liquid polymers, oils and the like), resins, flame-retardants,extender oils, lubricants, and a mixture of any of them. The general useand selection of such additives is well known to those skilled in theart. Their use in the system disclosed here will be readily understoodwith the benefit of the present disclosure.

[0054] The mixing zone/coagulum zone assembly is discussed in moredetail below. The elastomer masterbatch crumb is passed from thedischarge end of coagulum reactor 14 to suitable drying and compoundingapparatus. In the preferred embodiment of FIG. 1, the masterbatch crumbis passed first via conveying means 41 to a de-watering extruder 40. Inroutine preferred embodiments consistent with that illustrated in FIG. 1producing natural rubber masterbatch with carbon black filler, thede-watering operation will typically reduce water content from about70-80 weight percent, to about 15 - 25 weight percent. Water isdischarged from de-watering extruder 40 via effluent stream 43. Suitablede-watering extruders are well known and commercially available from,for example, the French Oil Machinery Co. (Piqua, Ohio, USA).

[0055] The masterbatch is passed from de-watering extruder 40 viaconveyor or simple gravity drop or other suitable means 101 to acontinuous compounder 100 and then to an open mill 120. In routinepreferred embodiments consistent with that illustrated in FIG. 1producing natural rubber masterbatch with carbon black filler, thecompounding and milling operation will typically reduce water contentfrom about 15-25 weight percent, to less than 1 weight percent. Incertain preferred embodiments, additives can be combined with themasterbatch in continuous compounder 100. Specifically, additives suchas antioxidants, antiozonants, plasticizers, processing aids (e.g.,liquid polymers, oils and the like), resins, flame-retardants, extenderoils, lubricants, and a mixture of any of them, can be added incontinuous compounder 100. In certain other preferred embodiments,additional elastomers can be combined with the masterbatch in continuouscompounder 100 to produce elastomer blends. Exemplary elastomersinclude, but are not limited to, rubbers, polymers (e.g., homopolymers,copolymers and/or terpolymers) of 1,3-butadiene, styrene, isoprene,isobutylene, 2,3-dimethyl-1,3-butadiene, acrylonitrile, ethylene, andpropylene and the like. Continuous compounder 100 dries the masterbatch,masticates the masterbatch, provides control of its Mooney Viscosity andmolecular weight, and minimizes the reduction of bound rubber. Suitablecontinuous compounders are well known and commercially available,including for example, the Unimix Continuous Mixer from FarrelCorporation of Ansonia, Conn.

[0056] As seen in FIGS. 1 and 8, the elastomer masterbatch is fed fromcoagulum reactor 14 to de-watering extruder 40 and then into feed port102 formed in an elongate processing chamber 104 of continuouscompounder 100. In certain preferred embodiments, feed port 102 is ahopper which facilitates a gravity drop of the elastomer masterbatchfrom de-watering extruder 40. Feed port 102 may also be fed via conveyormeans such as a conveyor belt, conduit, pipe, or any other suitablemeans for transporting elastomer masterbatch. Processing chamber 104 iscontained within housing 105 of continuous compounder 100. Elongaterotors 106 are seen to be parallel to each other and axially oriented inprocessing chamber 104. Rotors 106 are driven by motor 108 via gearreducer 110 and bearings 112. Rotors 106 are adapted in accordance withknown designs for processing material axially through elongateprocessing chamber 104. As seen in FIG. 8, multiple rotors 106 areaxially oriented in processing chamber 104. Rotors 106 preferably aresegmented, with different segments optionally having different thread orscrew configurations. In a preferred embodiment, processing chamber 104houses two rotors 106 having different profiles. Suitable rotors 106having different profiles include, for example, rotor model numbers 7and 15 from Farrel Corporation of Ansonia Conn. In a preferredembodiment, rotors 106 contain a fluid which can be temperaturecontrolled to provide heating and/or cooling to the elastomermasterbatch.

[0057] As seen in the embodiment illustrated in FIG. 8, each rotor 106has a first segment 116 and a second segment 118. As the elastomermasterbatch passes through processing chamber 104, the rotors masticatethe material, thereby mixing and drying the elastomer masterbatch. Port109 is provided in processing chamber 104 for the addition of liquidadditives. Dry materials can be added to the elastomer masterbatch viafeed port 102. Vent 111 is provided in processing chamber 104 to allowmoisture to vent as the elastomer masterbatch dries. The elastomermasterbatch exits processing chamber 104 via discharge orifice 114. Afirst temperature control device 115 provides heating and/or cooling tocontinuous compounder 100, typically with heated water. A secondtemperature control device 117 provides heating and/or cooling todischarge orifice 114, typically with chilled water. During a typicalprocess, heat is added during startup, and then, once the process isfully underway, heating is discontinued and cooling is applied. Duringstartup, heat is typically applied specifically to processing chamber104 and discharge orifice 114, and during operation, cooling is appliedspecifically to feed port 102, processing chamber 104 and rotors 106. Ina typical application, with a nominal throughput of 1000 lbs/hour ofelastomer masterbatch, approximately 250,000-500,000 BTU/hr may beremoved by cooling. As noted above, preferred embodiments of continuouscompounder 100 dry the masterbatch as well as controlling its MooneyViscosity and molecular weight, while not excessively reducing boundrubber. Certain preferred embodiments of continuous compounder 100 canreduce water content of the elastomer masterbatch from up toapproximately 25 weight percent, to less than approximately 1 weightpercent.

[0058] Control of the operating parameters of continuous compounder 100allows control of the Mooney Viscosity, moisture content, molecularweight and bound rubber of the elastomer masterbatch. Such operatingparameters include throughput rate of the continuous compounder, rotorspeed, discharge orifice size and temperature, and processing chambertemperature.

[0059] In certain preferred embodiments, the elastomer masterbatchdischarged from continuous compounder 100 is fed to open mill 120. Theelastomer masterbatch is discharged as a length of extrudate and may becut into smaller lengths prior to entering open mill 120. The elastomermasterbatch may optionally be fed to open mill 120 via conveyor 119.Conveyor 119 may be a conveyor belt, conduit, pipe, or other suitablemeans for transporting the elastomer masterbatch from continuouscompounder 100 to open mill 120. Open mill 120 comprises a pair ofrollers 122 which further control the Mooney Viscosity of the elastomermasterbatch. Rollers 122 may optionally be heated or cooled to provideenhanced operation of open mill 120. In certain embodiments, open mill120 may reduce the temperature of the elastomer masterbatchapproximately 1000C.

[0060] After exiting open mill 120, the elastomer masterbatch optionallymay be fed by conveyor 200 to cooling system 202, as seen in FIG. 9.Cooling system 202 may include a cooling water spray 204, with its waterbeing fed from cooling water tank 206 or other water source. The waterfrom cooling water spray 204 may be sprayed directly onto the elastomermasterbatch. In certain embodiments, an antistick agent, e.g., Promol,manufactured by Hans W. Barbe, of Germany, and containing silicates andcalcium stearate, may be added to the water spray or used in place ofthe water spray. Optionally, the elastomer masterbatch can then be fedby conveyor 208 to granulator 210. If cooling water spray 204 has beenused, optionally an air knife 212 or other high pressure air blower orother suitable means can be used to remove any cooling water that didnot evaporate from the elastomer masterbatch. The elastomer masterbatchcan then optionally be fed by conveyor 214 to a baler 216, where theelastomer masterbatch can be baled more or less tightly or densely byvarying the dwell time, that is, the pressure and time in baler 216,depending on its intended use. For example, a looser bale may bepreferred for use in a Banbury mixer or the like.

[0061] As indicated above, the continuous compounder embodying themethod and apparatus of the present invention is controllable so as tocontrol the change in Mooney Viscosity, molecular weight, bound rubber,and drying of the masterbatch processed in the continuous compounder.The degree of change and final value of the these parameters will beselected in accordance with the intended use application of theresultant masterbatch. It will be within the ability of those skilled inthe art, given the benefit of this disclosure, to select suitable rotordesigns, and rotor operating conditions and parameters, to control theMooney Viscosity, molecular weight, bound rubber and drying of theelastomer masterbatch processed in the continuous compounder. Typically,the Mooney Viscosity of masterbatch produced in the coagulum reactor ishigher than desired for certain end use applications. The continuouscompounder can advantageously reduce the Mooney Viscosity of themasterbatch to a selected lower value.

[0062]FIG. 8 schematically illustrates a subsystem 58 for introducingdry additives via conduit 171 and feed port 102 into continuouscompounder 100. Also schematically illustrated in FIG. 8 is subsystem 59for introducing liquid additives via conduit 172 and feed port 102 intocontinuous compounder 100. Conduits 171, 172, 173 may be, for example,pipes, conveyor belts, or other suitable means for transporting materialfrom the respective subsystem to continuous compounder 100. Exemplaryadditives include, for example, filler (which may be the same as, ordifferent from, the filler used in the coagulum reactor; exemplaryfillers including silica and zinc oxide, with zinc oxide also acting asa curing agent), other elastomers, other or additional masterbatch,antioxidants, antiozonants, plasticizers, processing aids (e.g., stearicacid, which can also be used as a curing agent, liquid polymers, oils,waxes, and the like), resins, flame-retardants, extender oils,lubricants, and a mixture of any of them. The addition of elastomers canproduce elastomer blends via continuous compounder 100. Exemplaryelastomers include, but are not limited to, rubbers, polymers (e.g.,homopolymers, copolymers and/or terpolymers) of 1,3-butadiene, styrene,isoprene, isobutylene, 2,3-dimethyl-1,3-butadiene, acrylonitrile,ethylene, and propylene and the like. It is to be appreciated that anycombination of elastomers, additives and second masterbatch may be addedin continuous compounder 100 to the elastomer masterbatch produced inthe coagulum reactor 14.

[0063] The dimensions and particular design features of the coagulumreactor 14, including the mixing zone/coagulum zone assembly, suitablefor an embodiment in accordance with FIG. 1, will depend in part on suchdesign factors as the desired throughput capacity, the selection ofmaterials to be processed, etc. One preferred embodiment is illustratedin FIG. 2 wherein a coagulum reactor 48 has a mixing head 50 attached toa coagulum zone 52 with a fluid-tight seal at joint 54. FIG. 2schematically illustrates a first subsystem 56 for feeding elastomerlatex to the mixing zone, subsystem 57 for feeding carbon black slurryor other particulate filler fluid to the mixing zone, and subsystem 58for feeding an optional additive fluid, pressurized air, etc. to themixing zone. The mixing head 50 is seen to have three feed channels 60,61, 62. Feed channel 60 is provided for the natural rubber latex fluidand feed channel 62 is provided for direct feed of gas and/or additivefluid. In connection with preferred embodiments employing directinjection of additives, significant advantage is achieved in connectionwith hydrocarbon additives or, more generally, non-water miscibleadditives. While it is well known to employ emulsion intermediates tocreate additive emulsions suitable for pre-blending with an elastomerlatex, preferred embodiments in accordance with the present disclosureemploying direct injection of additives can eliminate not only the needfor emulsion intermediates, but also the equipment such as tanks,dispersing equipment, etc. previously used in forming the emulsions.Reductions in manufacturing cost and complexity can, therefore, beachieved. As discussed farther below, the feed channel 61 through whichslurry is fed to the mixing zone is preferably coaxial with the mixingzone and the coagulum zone of the coagulum reactor. While only a singlefeed channel is shown to receive the elastomer latex fluid, any suitablenumber of feed channels may be arranged around the central feed channelthrough which the slurry is fed to the mixing zone. Thus, for example,in the embodiment of FIG. 2 a fourth feed channel could be providedthrough which ambient air or high pressure air or other gas is fed tothe mixing zone. Pressurized air may be injected likewise with theslurry through the central axial feed channel 61. Auxiliary feedchannels can be temporarily or permanently sealed when not in use.

[0064] The coagulum zone 52 of the coagulum reactor 48 is seen to have afirst portion 64 having an axial length which may be selected dependingupon design objectives for the particular application intended.Optionally, the coagulum zone may have a constant cross-sectional areaover all or substantially all of its axial length. Thus, for example,the coagulum reactor may define a simple, straight tubular flow channelfrom the mixing zone to the discharge end. Preferably, however, forreasons discussed above, and as seen in the preferred embodimentillustrated in the drawings, the cross-sectional area of the coagulumzone 52 increases progressively from the entry end 66 to discharge end68. More specifically, the cross-sectional area increases in thelongitudinal direction from the entry end to the discharge end. In theembodiment of FIG. 2, the coagulum zone increases in cross-sectionalarea progressively in the sense that it increases continuously followingconstant cross-sectional portion 64. References to the diameter andcross-sectional area of the coagulum reactor (or, more properly, thecoagulum zone defined within the coagulum reactor) and other components,unless stated otherwise, are intended to mean the cross-sectional areaof the open flow passageway and the inside diameter of such flowpassageway.

[0065] Elastomer composite, specifically, coagulated elastomer latex inthe form of masterbatch crumb 72, is seen being discharged from thecoagulum reactor 48 through a diverter 70. Diverter 70 is an adjustableconduit attached to the coagulum reactor at discharge end 68. It isadjustable so as to selectively pass the elastomer masterbatch crumb 72to any of various different receiving sites. This feature advantageouslyfacilitates removal of masterbatch crumb from the product stream, forexample, for testing or at the beginning of a production run wheninitial process instability may result temporarily in inferior product.In addition, the diverter provides design flexibility to direct productfrom the coagulum reactor to different post-processing paths. Inaccordance with the preferred embodiment of FIG. 1, the masterbatchcrumb 72 being discharged from coagulum reactor 48 through diverter 70is seen to be received by de-watering extruder 40 and from there fedinto continuous compounder 100 via feed port 102.

[0066] The cross-sectional dimension of coagulum reactor 48 is seen toincrease at an overall angle a between entry end 66 and discharge end68. Angle α is greater than 0° and in preferred embodiments is less than45°, more preferably less than 15°, most preferably from 0.5° to 5°. Theangle a is seen to be a half angle, in that it is measured from thecentral longitudinal axis of the coagulum zone to a point A at the outercircumference of the coagulum zone at the end of the coagulum reactor.In this regard, it should be understood that the cross-sectional area ofthe upstream portion of the coagulum reactor, that is, the portion nearthe entry end 66, preferably increases sufficiently slowly to achievequasi-molding of the coagulum in accordance with the principlesdiscussed above. Too large an angle of expansion of the coagulum zonemay result in the elastomer masterbatch not being produced in desirablecrumb form of globules or worms and simply spraying through the coagulumreactor. Increasing the bore of the coagulum reactor too slowly canresult, in certain embodiments, in backup or clogging of the feeds andreaction product into the mixing head. In a downstream portion of thecoagulum zone, wherein the latex has been substantially coagulated andflow has become essentially plug flow, the coagulum zone may extendeither with or without increase in cross-sectional area. Thus, referencehere to the coagulum zone in preferred embodiments having aprogressively increasing cross-sectional area should be understood torefer primarily to that portion of the coagulum zone wherein flow is notsubstantially plug flow.

[0067] The cross-sectional area of the coagulum zone (that is, at leastthe upstream portion thereof, as discussed immediately above) mayincrease in step-wise fashion, rather than in the continuous fashionillustrated in the embodiment of FIG. 2. In the embodiment illustratedin FIG. 3, a continuous flow system for production of elastomermasterbatch in accordance with the method and apparatus disclosed here,is seen to include a mixing head/coagulum zone assembly wherein thecross-sectional area of the coagulum zone increases in step-wisefashion. Preferably, the individual sections of the coagulum zone insuch a step-wise embodiment have a flared connection to adjacentsections. That is, they combine to form a smooth and generallycontinuous coagulum zone surface, as opposed, for example, to a sharp orinstantaneous increase in diameter from one section to the next. Thecoagulum zone of FIG. 3 increases in three steps, such that there arefour different sections or sub-zones 74-77. Consistent with the designprinciples discussed immediately above, the cross-sectional area ofcoagulum zone 53 increases from the entry end 66 to point A at thedischarge end 68 at an overall angle which achieves the necessary flowcontrol in the upstream portion of the coagulum reactor. The firstsection 74 can be taken as including (a) the constant diameter portionof the mixing head 50 immediately downstream of the mixing zone, and (b)the same or similar diameter portion connected thereto at joint 54 atthe entry end 66. This first section has a constant cross-sectionaldiameter D₁ and an axial dimension or length L₁. In this first section74 the length L₁ should be greater than three times the diameter D₁,more preferably greater than five times D₁ and most preferably fromabout 12 to 18 times D₁. Typically, this section will have a length ofabout fifteen times D₁. Each subsequent section preferably has aconstant cross-sectional dimension and cross-sectional areaapproximately double that of the preceding (i.e., upstream) section.Thus, for example, section 75 has a constant cross-sectional dimensionand a cross-sectional area which is twice that of section 74. Similarly,the cross-sectional area of section 76 is double that of section 75, andthe cross-sectional area of section 77 is double that of section 76. Ineach of sections 75-77, the length is preferably greater than threetimes its diameter, more preferably about three to seven times itsdiameter and generally about five times its diameter. Thus, for example,in section 76 longitudinal dimension L₃ is preferably about five timesits diameter D₃.

[0068] A mixing head and coagulum zone assembly corresponding to theembodiment of FIG. 3 is shown in FIG. 4 partially in section view.Mixing head 50 is integral with coagulum zone extender 53 via joint 54.It defines a mixing zone wherein multiple feed channels 60, 61, 62 forma junction, with an elongate, substantially cylindrical channel 80substantially coaxial with the coagulum zone portion within extender 53.It will be recognized that it is not essential to the operability of themethod and apparatus disclosed here, to precisely define the boundariesof the mixing zone and/or coagulum zone. Numerous variations arepossible in the design of the flow channels junction area, as will beapparent to those skilled in the art given the benefit of the presentdisclosure. In that regard, as a generally preferred guideline, inembodiments of the type illustrated in FIG. 4, for example, the slurrytip 67 generally is upstream of the beginning of cylindrical portion 80,being approximately centered longitudinally in the junction of the feedchannels. In such embodiments, preferably, the minimum cross-sectionalarea defined by the imaginary cone from the slurry tip 67 to thecircumferential perimeter at the beginning of the cylindrical portion 80is advantageously greater than, or at least equal to, thecross-sectional area of the latex feed channel 60. Preferably, bothchannel 80 and at least the upstream portion of the coagulum zonewherein flow turbulence exists prior to substantially completecoagulation of the elastomer latex, have a circular cross-section.

[0069] The means for feeding carbon black slurry or other particulatefiller fluid is seen to comprise a feed tube 82 extending substantiallycoaxially with the mixing chamber to an opening or slurry nozzle tip 67which is open toward the coagulum zone. This is a highly advantageousfeature of the preferred embodiments discussed here. The carbon blackslurry, as noted above, is fed to the mixing zone at very high velocityrelative the feed velocity of the latex, and the axial arrangement ofnarrow bore feed tube 82 results in excellent development of flowturbulence. The diameter D_(m) of the channel 80 (which, as noted above,is preferably substantially equal to the diameter D₁ of immediatelyfollowing portion of section 74 of the coagulum zone) preferably is atleast twice the inside diameter of slurry feed tube 82, more preferablyabout four to eight times the diameter of feed tube 82, typically aboutseven to eight times that diameter. Feed tube 82 is seen to form afluid-tight seal with the entry port 83 at the upstream end of feedchannel 61 of mixing head 50. The diameter of the axial feed tube 82 isdetermined largely by the required volumetric flow rate and axialvelocity of the slurry as it passes through the slurry nozzle tip 67into the mixing chamber. The correct or required volume and velocity canbe readily determined by those skilled in the art given the benefit ofthis disclosure, and will be a function, in part, of the concentrationand choice of materials. Embodiments such as that illustrated anddisclosed here, wherein the feed tube for the carbon black slurry isremovable, provide desirable flexibility in manufacturing differentmasterbatch compositions at different times. The feed tube used in oneproduction run can be removed and replaced by a larger or smaller boretube appropriate to a subsequent production. In view of the pressure andvelocity at which the slurry exits the feed tube, it may be referred toas a spray or jet into the mixing zone. This should be understood tomean in at least certain embodiments, high speed injection of the slurryinto an area already substantially filled with fluid. Thus, it is aspray in the sense of its immediate distribution as it passes throughthe slurry nozzle tip, and not necessarily in the sense of free-flyingmaterial droplets in a simple spreading trajectory.

[0070] The additional feed channels 60 and 62 are seen to form ajunction 84, 85, respectively, with feed channel 60 and downstreamchannel 80 at an angle β. The angle β may in many embodiments have avalue from greater than 0° to less than 180°. Typically, β may be, forexample, from 30°-90°. It is desirable to avoid a negative pressure,that is, cavitation of the latex fluid as it is entrained by the highvelocity slurry exiting at slurry nozzle tip 67, since this maydisadvantageously cause inconsistent mixing leading to inconsistentmasterbatch product. Air or other gas can be injected or otherwise fedto the mixing zone to assist in breaking any such vacuum. In addition,an expanded feed line for the natural rubber latex leading to the entryport 86 of feed channel 60 is desirable to act as a latex fluidreservoir. In the preferred embodiment of FIG. 4, latex feed channel 60intersects the mixing zone adjacent slurry nozzle tip 67. Alternatively,however, the latex feed channel can intersect the mixing channelupstream or downstream of the slurry nozzle tip 67.

[0071] The carbon black slurry or other particulate filler fluidtypically is supplied to feed tube 82 at a pressure above about 300psig, such as about 500 to 5000 psig, e.g. about 1000 psig. Preferablythe liquid slurry is fed into the mixing zone through the slurry nozzletip 67 at a velocity above 100 ft. per second, preferably about 100 toabout 800 ft. per second, more preferably about 200 to 500 ft. persecond, for example, about 350 feet per second. Arrows 51 in FIG. 4represent the general direction of flow of the elastomer latex andauxiliary feed materials through feed channels 60 and 62 into thechannel 80 below slurry nozzle tip 67. Thus, the slurry and latex fluidsare fed to the mixing zones at greatly different feed stream velocities,in accordance with the numbers set forth above. While not wishing to bebound by theory, it presently is understood that the differential feedachieves latex shear conditions in the mixing zone leading to goodmacro-dispersion and coagulation.

[0072] An alternative preferred embodiment is illustrated in FIGS. 5 and6 wherein the single axial feed tube 82 in the embodiment of FIG. 4 isreplaced by multiple axially extending feed tubes 90-92. Even greaternumbers of feed tubes may be employed, for example, up to about 6 or 8axially-extending feed tubes. Advantageously, production flexibility isachieved by using different feed tubes of different diameter forproduction of different formulations. Also, multiple feed tubes can beused simultaneously to achieve good flow turbulence within the mixingzone and coagulum zone of the coagulum reactor.

[0073] An alternative embodiment of the mixing head is illustrated inFIG. 7. Mixing head 150 is seen to define a mixing zone 179. An axialfeed channel 161 receives a feed tube 182 adapted to feed carbon blackslurry or other particulate filler fluid at high velocity into themixing chamber 179. It can be seen that the central bore in feed tube182 terminates at slurry nozzle tip 167. A constant diameter nozzle land168 is immediately upstream of slurry nozzle tip 167, leading to alarger bore area 169. Preferably the axial dimension of land 168 isabout 2 to 6, e.g. about 5, times its diameter. A second feed channel160 forms a junction 184 with the mixing zone 179 at a 90° angle forfeeding elastomer latex fluid to the mixing zone. The cross-sectionaldiameter of the latex fluid feed channel 160 is substantially largerthan the cross-sectional diameter of the slurry nozzle tip 167 and land168. Without wishing to be bound by theory, the axial elongation ofnozzle land 168, coupled with the expanded diameter bore sectionupstream of the nozzle land, is believed to provide advantageousstability in the flow of slurry through feed tube 182 into the mixingzone 179. The bore of feed tube 182 is found to function well with a 20°chamfer, that is, conical area 169 which expands in the upstreamdirection at about a 20° angle. Downstream of mixing zone 179 is anelongate coagulum zone. Consistent with the principles discussed above,such coagulum zone need be only marginally elongate. That is, its axialdimension need be only marginally longer than its diameter. Preferably,however, a progressively enlarged coagulum zone is used.

[0074] As discussed above, coagulation of the elastomer masterbatch issubstantially complete at or before the end of the coagulum reactor.That is, coagulation occurs within the coagulum zone of the coagulumreactor without the necessity of adding a stream of coagulant solutionor the like. This does not exclude the possibility that some initialcoagulation occurs in the mixing zone. The mixing zone may be consideredan extended portion of the coagulum zone for this purpose. Also,reference to substantially complete coagulation prior to the elastomermasterbatch exiting the coagulum reactor is not meant to exclude thepossibility of subsequent processing and follow-on treatment steps, forany of various purposes appropriate to the intended use of the finalproduct. In that regard, substantially complete coagulation in preferredembodiments of the novel method disclosed here employing natural rubberlatex means that at least about 95 weight percent of the rubberhydrocarbon of the latex is coagulated, more preferably at least about97 weight percent, and most preferably at least about 99 weight percentis coagulated.

[0075] The method and apparatus disclosed and described here produceelastomer composites having excellent physical properties andperformance characteristics. Novel elastomer composites of the presentinvention include masterbatch compositions produced by theabove-disclosed method and apparatus, as well as intermediate compoundsand finished products made from such masterbatch compositions. Notably,elastomer masterbatch can be produced using natural rubber latex (latexconcentrate or field latex), along with various grades of carbon blackfiller, having excellent physical properties and performancecharacteristics. Carbon blacks presently in broad commercial use forsuch application as tire tread have been used successfully, as well ascarbon blacks heretofore considered unsuitable for commercial use inknown production apparatus and methods. Those unsuitable because theirhigh surface area and low structure rendered them impractical to achieveacceptable levels of macro-dispersion at routine commercial loadinglevels for the carbon black and/or to preserve the molecular weight ofthe elastomer are highly preferred for the novel elastomeric masterbatchcompositions disclosed here. Such elastomer composites are found to haveexcellent dispersion of the carbon black in the natural rubber,controlled Mooney Viscosity and moisture level, together with goodpreservation of the molecular weight of the natural rubber. Moreover,these advantageous results were achieved without the need for acoagulation step involving a treatment tank or stream of acid solutionor other coagulant. Thus, not only can the cost and complexity of suchcoagulant treatments be avoided, so too the need to handle effluentstreams from such operations.

[0076] Prior known dry mastication techniques could not achieve equaldispersion of such fillers without significant molecular weightdegradation, nor was the Mooney Viscosity of the masterbatch controlledto a desired level and, therefore, could not produce the novel naturalrubber masterbatch compositions made in accordance with certainpreferred embodiments of the present invention. In that regard, novelelastomer composites are disclosed having excellent macro-dispersion ofthe carbon black in the natural rubber and controlled Mooney Viscosityand moisture level, even of carbon blacks having a structure to surfacearea ratio DBPA:CTAB less than 1.2 and even less than 1.0, with highmolecular weight of the natural rubber. Known mixing techniques in thepast did not achieve such excellent macro-dispersion of carbon blackwithout significant molecular weight degradation of the natural rubberand, therefore, did not produce the novel masterbatch compositions andother elastomer composites of the present invention. Preferred novelelastomer masterbatch compositions in accordance with this disclosure,having carbon black macro-distribution levels and controlled MooneyViscosity levels not heretofore achieved, can be used in place of priorknown masterbatch having poorer macro-dispersion. Thus, masterbatchdisclosed here can be incorporated into cured compounds in accordancewith known techniques. Such novel cured compounds are found in preferredembodiments to have physical characteristics and performance propertiesgenerally comparable to, and in some instances significantly betterthan, those of otherwise comparable cured compounds comprisingmasterbatch of poorer macro-dispersion. Masterbatch can be produced inaccordance with the present invention, however, with reduced mixingtime, reduced energy input, and/or other cost savings.

[0077] Particularly with respect to certain preferred embodiments,natural rubber latex and carbon black filler masterbatch can be producedhaving excellent physical characteristics and performance properties.Excellent macro-dispersion of the carbon black is achieved, even usingcarbon blacks of exceptionally high surface area and low structure,without the degree of degradation of the natural rubber which would becaused by dry mastication for sufficient time and at sufficientintensity levels to achieve the same degree of carbon black dispersion.Especially advantageous in this regard are novel natural rubbermasterbatch compositions wherein a high degree of dispersion isachieved, using carbon blacks having structure to surface area ratio,DBPA: CTAB of less than 1.2 and even less than 1.0. As used here, thecarbon black structure can be measured as the dibutyl phthalateadsorption (DBPA) value, expressed as cubic centimeters of DBPA per 100grams carbon black, according to the procedure set forth in ASTM D2414.The carbon black surface area can be measured as CTAB expressed assquare meters per gram of carbon black, according to the procedure setforth in ASTM D3765-85. Novel natural rubber masterbatch is achieved,therefore, having heretofore unachievable combinations of physicalcharacteristics such as molecular weight distribution and fillerdispersion levels, and/or incorporating heretofore unsuitable fillerssuch as carbon black of extraordinarily high surface area and lowstructure. The dispersion quality of natural rubber masterbatch producedin accordance with the methods and apparatus disclosed here can bedemonstrated with reference to the well known characteristics ofMW_(sol) (weight average) and macro-dispersion. Specifically, themacro-dispersion level in masterbatch produced in accordance withpreferred embodiments is significantly better than that in masterbatchof approximately equal MW_(sol) produced using dry mastication. Mostnotably, the dispersion quality of these preferred embodiments does notdepend significantly on the morphology of the carbon black filler. Itwill be recognized that other factors affecting the level of dispersionachievable using the method and apparatus disclosed here, include theconcentration of the carbon black in the slurry, total energy input intothe slurry and energy input during mixing of the fluid streams, etc.

[0078] The macro-dispersion quality of carbon black in natural rubbermasterbatch disclosed here is significantly better than that inpreviously known masterbatch of approximately equal MW_(sol) (weightaverage). In some preferred embodiments of novel elastomer composites,excellent carbon black distribution is achieved with MW_(sol)approximately that of natural rubber in the field latex state, (e.g.,approximately 1,000,000) a condition not previously achieved. Thedispersion quality advantage is especially significant in the abovementioned preferred embodiments using carbon black with low structureand high surface area, e.g., DBPA less than 110 cc/100 g, CTAB greaterthan 45 to 65 m²/g, and DBPA:CTAB less than 1.2 and preferably less than1.0.

[0079] The methods and apparatus of the present invention provideelastomer masterbatch improved commercial value of the masterbatch.Controlling the Mooney Viscosity and moisture level of the elastomermasterbatch provides a product which is better suited for certainpreferred end use applications. Employing the continuous compounderreduces or even eliminates the need for further mastication indownstream processes at end user facilities. Providing additionalelastomers, additives and masterbatch within the continuous compoundereliminates additional processing steps at end user facilities where themasterbatch is used to produce end products.

[0080] The methods and apparatus of the present invention can be used toform products which include, but are not limited to tires, tire treads,tire sidewalls, wire-skim for tires, cushion gum for retread tires,rubber components of engine mounts, tank tracks, mining belts, rubbercomponents of hydro-mounts, bridge bearings, and seismic isolators.

[0081] Results of experiments using the invention disclosed hereinfollow, wherein “FCM” represents the continuous compounder, or FarrelUnimix Continuous Mixer, and “OM” represents the open mill:

[0082] Trial #1 Data

[0083] This trial was conducted to test the drying capability of thecontinuous compounder (FCM). This trial was also designed to test thecapability to add and incorporate a stream of oil. This wet sample wasmade from natural rubber latex concentrate and N351 type carbon black.The masterbatch was fed into the continuous compounder with a moisturelevel of approximately 20 weight percent. CB Oil Rate Loading Loading(lb/hr Orifice Product Moisture Bound Sample (phr) (phr) dry) RPM (%)Temp (F.) (%) MV MW Rubber Bin #1 initial 35 — — — — — ^(˜)20 112.5 762K49.77 product Bin #2 initial 35 — — — — — ^(˜)20 110.1 740K 44.94product #1 34 17 465 500 33 275 1.32 68.7 681K 31.55 #2 35 18 372 500 23300 0.70 68.6 692K 33.64 #3 34 18 372 510 17 315 0.14 68.2 687K 37.28 #4— 17 372 510 17 330 0.40 66.2 672K 32.63 #5 34 20 419 450 32 306 0.3965.6 702K 34.68

[0084] Trial #2 Data

[0085] This trial was conducted to test the drying capability of thecontinuous compounder (FCM). This trial was also designed to test thecapability to add and incorporate a stream of oil. This wet sample wasmade from natural rubber field latex and N220 type carbon black. Themasterbatch was fed into the continuous compounder with a moisture levelof approximately 25 weight percent. CB Oil Rate Product Loading Loading(lb/hr Orifice Temp (F.) Moisture Bound Sample (phr) (phr) dry) RPM (%)max (%) MV MW Rubber Bin #1 initial 54 — — — — — ^(˜)25 196.0 707K 76.63product Bin #2 initial — — — — — — ^(˜)25 160.9 723K 75.84 product #1254 4 400 425 35 325 0.25 135.4 537K 72.79 #13 54 3 336 375 38 340 0.08135.9 510K 70.11

[0086] Trial #3 Data

[0087] This trial was conducted to test the drying capability of thecontinuous compounder (FCM). The open mill (OM) was also incorporatedinto this trial. This trial was also designed to test the capability toadd and incorporate streams of oil, stearic acid (SA), and anantioxidant (Santoflex 6PPD). This wet sample was made from naturalrubber field latex and Cabot experimental carbon black A. Themasterbatch was fed into the continuous compounder with a moisture levelof approximately 22 weight percent. SA/ CB Oil 6PPD Rate Loading LoadingLoading (lb/hr Orifice Sample (phr) (phr) (phr) dry) RPM (%) initial 50— — — — — product 6A OM 49 — — — — — 7A FCM 49 — 2/1 302 260 42 7A OM —— 7 217 — — 8A FCM 46 5 2/1 312 265 41 8A OM — 5 2/1 200 — — MaximumProduct Temp (F.) Moisture Bound Macro- Sample max (%) MV MW RubberDispersion initial — ^(˜)22 194 609K 77.81 A-4/0.30 product 6A OM — —171 332K 69.30 A-4/0.06 7A FCM 350 0.25 157 517K 74.66 A-4/0.13 7A OM190 0.35 135 386K 66.84 — 8A FCM 320 0.58 138 496K 70.83 A-4/0.10 8A OM— 0.61 118 440K 56.82 —

[0088] Trial #4 Data

[0089] This trial was conducted to test the drying capability of thecontinuous compounder (FCM). The open mill (OM) was also incorporatedinto this trial. This trial was also designed to test the capability toadd and incorporate streams of oil, stearic acid (SA), silica, and anantioxidant (Santoflex 6PPD). This wet sample was made from naturalrubber field latex and N220 type carbon black. The masterbatch was fedinto the continuous compounder with a moisture level of approximately 25weight percent. SA/ CB Oil Silica 6PPD Rate Loading Loading LoadingLoading (lb/hr Orifice Sample (phr) (phr) (phr) (phr) dry) RPM (%)initial 53 — — — — — — product 1A FCM 53 — — — 500 450 42 1A OM — — — —240 — — 2C FCM 53 8.5 — — 453 485 35 2C OM 55 8.5 — — 380 — — 3A FCM 528.5 — 3.1/ 487 500 40 3.1  3A OM 51 8.5 — 3.1/ 540 — — 3.1  5A FCM 528.5 8 3.1/ 470 490 41 3.1  5A OM 51 8.5 8 3.1/ 540 — — 3.1  MaximumBound Product Moisture Rubber Macro- Sample Temp (F.) (%) MV MW %Dispersion initial — ^(˜)25 154 688K 55.79 B-5/0.40 product 1A FCM —1.27 148 536K 69.33 A-4/0.07 1A OM 200 0.23 134 493K 69.44 — 2C FCM 3200.39 98 557K 60.62 A-3/0.03 2C OM 240 0.22 108 494K 66.91 A-3/0.09 3AFCM 340 0.06 90 610K 36.31 A-3/0.02 3A OM 210 0.25 90 636K 42.61A-4/0.11 5A FCM 330 0.24 103 573K 51.70 B-4/0.33 5A OM 210 0.34 90 552K48.67 A-4/0.20

[0090] Trial #5 Data

[0091] This trial was conducted to test the drying capability of thecontinuous compounder (FCM). The open mill (OM) was also incorporatedinto this trial. This wet sample was made from natural rubber fieldlatex and N234 type carbon black. The masterbatch was fed into thecontinuous compounder with a moisture level of approximately 24 weightpercent. CB Rate Maximum Loading (lb/hr Orifice Product Sample (phr)dry) RPM (%) Temp (F.) initial 51 — — — — product FC1 FCM 52 300 250 44340 FC1 OM 52 — — —— Bound Moisture Rubber Macro- Sample (%) MV MW %Dispersion initial ^(˜)24 218 645K 72.21 A-4/0.18 product FC1 FCM 0.50160 467K 69.36 A-3/0.03 FC1 OM 0.15 141 335K 63.55 A-4/0.12

[0092] Trial #6 Data

[0093] This trial was conducted to test the drying capability of thecontinuous compounder (FCM). The open mill (OM) was also incorporatedinto this trial. This trial was also designed to test the capability toadd and incorporate streams of oil, stearic acid (SA), zinc oxide (ZnO),silica, and an antioxidant (Santoflex 6PPD). The feasibility of addingbutadiene rubber was also investigated for sample FA4 during this trial.This wet sample was made from natural rubber field latex and N220 typecarbon black. The masterbatch was fed into the continuous compounderwith a moisture level of approximately 20 weight percent. SA/ 6PPD/ CBOil Silica ZnO Rate Loading Loading Loading Loading (lb/hr OrificeSample (phr) (phr) (phr) (phr) dry) RPM (%) initial 74 — — — — — —product FA3 FCM — 7.9 7.1 2.9/ 400 300 59 2.9/ 5.0  FA3 OM 73 7.9 7.12.9/ — — — 2.9/ 5.0  FA4 FCM — 5.5 5.0 2.0/ 400 300 48 2.0/ 3.5  FA4 OM55 5.5 5.0 2.0/ — — — 2.0/ 3.5  Maximum Bound Product Moisture RubberMacro- Sample Temp (F.) (%) MV MW % Dispersion initial — ^(˜)20 >200611K 70.74 A-3/0.10 product FA3 FCM 335 0.37 154 483K 70.71 A-3/0.10 FA3OM — 0.14 133 362K 54.58 A-4/0.17 FA4 FCM 330 0.63 125 370K 44.08 — FA4OM — 0.19 113 376K 43.68 C-6/1.36

[0094] Trial #7 Data

[0095] This trial was conducted to test the drying capability of thecontinuous compounder (FCM). The open mill (OM) was also incorporatedinto this trial. This trial was also designed to test the capability toadd and incorporate streams of oil, stearic acid (SA), zinc oxide (ZnO),silica, and an antioxidant (Santoflex 6PPD). This wet sample was madefrom natural rubber field latex and N220 type carbon black. Themasterbatch was fed into the continuous compounder with a moisture levelof approximately 24 weight percent. SA/ 6PPD/ CB Oil Silica ZnO RateLoading Loading Loading Loading (lb/hr Orifice Sample (phr) (phr) (phr)(phr) dry) RPM (%) initial 53 — — — — — — product FB1 FCM 53 8.5 — 3.1/400 410 39 3.1  FB1 OM 54 8.5 — 3.1/ — — — 3.1  FB2 FCM 53 8.5 7.7 3.1/400 330 49 3.1/ 5.4  FB2 OM 53 8.5 7.7 3.1/ — — — 3.1/ 5.4  Max BoundProduct Moisture Rubber Macro- Sample Temp (F.) (%) MV MW % Dispersioninitial — ^(˜)24 189 751K 63.42 A-3/0.09 product FB1 FCM 339 0.45 84671K 41.04 A-3/0.07 FB1 OM — 0.31 86 600K 43.91 A-4/0.06 FB2 FCM 3420.44 78 609K 49.85 A-4/0.14 FB2 OM — 0.26 80 468K 49.34 A-4/0.17

[0096] In view of the foregoing disclosure, it will be apparent to thoseskilled in the art that various additions, modifications, etc. can bemade without departing from the true scope and spirit of the invention.All such additions and modifications are intended to be covered by thefollowing claims.

We claim:
 1. A method of treating a substantially coagulated masterbatch comprising a particulate filler and an elastomer, the method comprising the steps of: feeding the masterbatch to a feed port of a continuous compounder having multiple rotors axially oriented in an elongate processing chamber; processing the masterbatch through the processing chamber of the continuous compounder by controlled operation of the rotors; and discharging the masterbatch from a discharge orifice of the continuous compounder.
 2. The method of claim 1, further comprising the step of passing the masterbatch from the discharge orifice of the continuous compounder through an open mill.
 3. The method of claim 2, further comprising the steps of passing the masterbatch from the open mill through a cooling system having a water spray, passing the masterbatch form the cooling system through a granulator, and passing the masterbatch from the granulator through a baler.
 4. The method of claim 1, further comprising the step of compounding additional material into the masterbatch in the continuous compounder.
 5. The method of claim 4, wherein the additional material is selected from additional filler, additional elastomer, a second masterbatch, oil and other additives.
 6. The method of claim 1, wherein the continuous compounder dries the masterbatch.
 7. The method of claim 1, wherein the continuous compounder controls the Mooney Viscosity of the masterbatch.
 8. A continuous flow method of producing elastomer composite, comprising: feeding a continuous flow of first fluid comprising elastomer latex to a mixing zone of a coagulum reactor defining an elongate coagulum zone extending from the mixing zone to a discharge end; feeding a continuous flow of second fluid comprising particulate filler under pressure to the mixing zone of the coagulum reactor to form a mixture with the elastomer latex, the mixture passing as a continuous flow to the discharge end and the particulate filler being effective to coagulate the elastomer latex, wherein mixing of the first fluid and the second fluid within the mixing zone is sufficiently energetic to substantially completely coagulate the elastomer latex with the particulate filler prior to the discharge end; discharging a substantially continuous flow of elastomer composite from the discharge end of the coagulum reactor; feeding the substantially continuous flow of elastomer composite to a feed port of a continuous compounder having multiple parallel rotors axially oriented in an elongate processing chamber; processing the elastomer composite through the processing chamber of the continuous compounder by controlled operation of the rotors; and discharging the elastomer composite from a discharge orifice of the continuous compounder.
 9. The method of claim 8, further comprising the step of processing the elastomer composite from the discharge orifice of the continuous compounder through an open mill.
 10. The method of claim 9, further comprising the steps of passing the masterbatch from the open mill through a cooling system having a water spray, passing the masterbatch from the cooling system through a granulator, and passing the masterbatch from the granulator through a baler.
 11. Apparatus for producing elastomer composite of particulate filler dispersed in elastomer, comprising: a coagulum reactor defining a mixing zone and an elongate coagulum zone extending from the mixing zone to a discharge end; latex feed means for feeding elastomer latex fluid continuously to the mixing zone; filler feed means for feeding particulate filler fluid as a continuous jet into the mixing zone to form a mixture with the elastomer latex fluid traveling from the mixing zone to the discharge end of the coagulum zone, wherein the distance between the mixing zone and the discharge end is sufficient to permit substantially complete coagulation of the elastomer latex prior to the discharge end; and a continuous compounder having a feed port operatively connected to the discharge end of the coagulum zone for receiving the coagulated mixture of elastomer latex and particulate filler, a discharge orifice, an elongate processing chamber, and a plurality of rotors axially oriented within the processing chamber.
 12. The apparatus of claim 11, further comprising conveying means for conveying a substantially continuous flow of elastomer composite from the discharge end of the coagulum zone to the feed port of the continuous compounder.
 13. The apparatus of claim 11, further comprising: an open mill connected by a conveyor to the discharge orifice of the continuous compounder; a cooling system having a water spray and connected by a conveyor to the open mill; a granulator connected by a conveyor to the cooling system; and a baler connected by a conveyor to the granulator.
 14. An elastomer composite comprising substantially coagulated elastomer in which particulate filler has been dispersed by: feeding a continuous flow of first fluid comprising elastomer latex to a mixing zone of a coagulum reactor defining an elongate coagulum zone extending from the mixing zone to a discharge end; feeding a continuous flow of second fluid comprising particulate filler under pressure to the mixing zone of the coagulum reactor to form a mixture with the elastomer latex, the mixture passing as a continuous flow to the discharge end, and the particulate filler being effective to coagulate the elastomer latex, wherein mixing of the first fluid and the second fluid within the mixing zone is sufficiently energetic to substantially completely coagulate the elastomer latex with the particulate filler prior to the discharge end; discharging a substantially continuous flow of elastomer composite from the discharge end of the coagulum reactor; feeding the elastomer composite from the discharge end of the coagulum reactor to a continuous compounder having multiple parallel elongate rotors axially oriented in an elongate processing chamber; processing the masterbatch through the processing chamber of the continuous compounder by controlled operation of the rotors; and discharging the masterbatch from a discharge orifice of the continuous compounder. 